Conventionally, optical modules for optical communication can be classified into two types, a coaxial pigtail type, which is based on a can type and in which an optical waveguide, e.g., an optical fiber, and a semiconductor optical element are connected optically to each other through a lens, and a receptacle type in which an optical fiber can be attached or detached by means of a connector. Further, pump lasers or laser diode modules of a distribution-feedback type for optical fiber amplifiers include butterfly-type pigtail modules that include a cooler using a Peltier element. In order to obtain high reliability, in this case, the modules of the two types employ a hermetically sealed structure of metal or ceramics. An optical waveguide component, e.g., an optical fiber, receives light from a light emitting element, and is fixed to a module by soldering or YAG-laser welding when the quantity of light projected with the optical fiber being aligned attains a desired value.
On the other hand, optical modules of a new type have been developed in order to meet a demand for the reduction of costs to realize modern optical subscriber systems. An example is disclosed in the Telecommunications Society-Electronics Society Meeting Drafts C-296, 1996, for instance.
This optical module is characterized by being of a plane mounting type such that a dual inline (DIL) is used for a package.
In this optical module, a laser diode (hereinafter referred to as "LD") is mounted highly accurately on a silicon substrate through picture recognition. A short optical waveguide component, such as an optical fiber, is fixed nonaligned by utilizing a V-groove on the side of light emission from the LD of the substrate. This optical module can be easily sealed by means of a resin adhesive agent. An end portion of the optical fiber may be of a detachable type based on a connector interface or of a pigtail type.
However, the aforesaid module has the following problems. In order to couple the optical waveguide component, such as an optical fiber, accurately to an optical element, the V-groove(s) of the silicon substrate must be worked with high accuracy of about 0.5 .mu.m. If the optical fiber is a single fiber, the silicon substrate requires only one V-groove. In the case where a plurality of optical fibers are coupled to a plurality of semiconductor optical elements, however, a plurality of V-grooves must be worked with high accuracy.
Conventionally, a wet-etching method based on a potassium hydroxide solution or the like is used to work V-grooves on silicon substrates.
According to this method, however, the substrates are etched very dispersedly, so that it is hard uniformly to work fine V-grooves. In the case where a plurality of V-grooves are all worked uniformly, in particular, the yield of the resulting substrates is low. Moreover, the optical fibers, e.g., single-mode fibers, are fine, having diameters as small as about 125 .mu.m, so that they cannot be handled with ease when they are positioned in the V-grooves of the silicon substrate. In positioning a plurality of optical fibers, such as tape fibers, in their corresponding V-grooves, in particular, the optical fibers are arranged so disorderly that they cannot be easily fixed to the V-grooves unless force is applied equally to every optical fiber.
The present invention has been contrived in consideration of these circumstances, and its object is to provide optical modules, which can be assembled with ease and of which substrates can be manufactured with good yield, whereby optical waveguide components, such as optical fibers, and semiconductor optical elements are coupled optically.